Compensating hydraulic stabilizing system for bulldozer



l 1969 G. A. 'DRONE 1 3,441,092

COMPENSATING HYDRAULIC STABILIZING SYSTEM FOR BULLDOZER Filed Nov. 7. 1966 I ,1; M (M pzmw United States Patent Wis.

Filed Nov. 7, 1966, Ser. No. 592,538 Int. Cl. E02f 3/ 85 US. Cl. 172-803 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a hydraulic stabilizing system for a dozer and push beams which prevents the introduction of stresses due to tilting operations, while still maintaining lateral stability of the blade.

In conventional bulldozer design a blade is pivotally connected to the front ends of a pair of push beams which in turn have their rear ends pivotally connected to a tractor for vertical swinging movement to raise and lower the blade. A pair of diagonal braces in a horizontal plane interconnect the push beams and blade to prevent sidewise movement of the blade. A pair of tilt struts extend diagonally upward from the push beams to the blade to hold it in its normal upright position and by varying the length of one or both of the tilt struts, the blade is tilted to achieve a sloping cut during operation of the bulldozer tractor. When a tilt strut is extended or contracted to tilt the blade, the associated push beam is rotated in a plane substantially perpendicular to the blade about the push beam pivot connection with the tractor. If it were not for the rear ends of the push beams being connected to the tractor they would be displaced outwardly from one another. Since the rear ends of the push beams cannot be displaced from one another, the push beams and blade are subjected to bending forces and the diagonal braces are subjected to considerable compressive loading. In actual tilt blade operations the push beams are deflected under the bending forces and are vulnerable to damage or breakage when the blade is subjected to side thrust.

Heretofore others have suggested the use of mechanical linkages and mechanisms, such as shown in US. patents numbered 3,025,620, 3,049,820, 3,049,821 and 3,187,448 to obviate the problems hereinbefore discussed, however, these are subject to breakage and damage from foreign material and are subject to malfunction from stone or rock particles wedging between components or otherwise detrimentally affecting the desired operation.

This invention overcomes the beforementioned difiiculties in an entirely satisfactory manner by use of a pair of hydraulically interconnected double acting jacks in the diagonal braces.

It is an object of this invention to provide diagonal bracing for a bulldozer blade which obviates the hereinbefore outlined difliculties.

It is a further object of this invention to provide an improved bulldozer having diagonal bracing which affords lateral stabilization for the blade but avoids loading up the push beams and other components with excessive forces during tilted blade operations.

It is a further object of this invention to provide tilt compensating diagonal braces for a bulldozer blade which employ interconnected hydraulic jacks.

These and other objects and advantages of this invention will be apparent to those familiar with the related art when the following description is read in conjunction with the drawings in which:

3,441,092 Patented Apr. 29, 1969 FIG. 1 is a top view of a bulldozer in which the present invention is used; and

FIG. 2 is an elevation view of the bulldozer shown in FIG. 1.

The drawings illustrate a bulldozer attachment having a pair of laterally spaced push beams 11, 12, the rear ends of which are universally connected to pivot ball members 13, 14 and the front ends of which are pivotally connected on a transverse pivot axis 16 to the bottom rear of a dozer blade 17 by pins 18, 19.

A pair of extensible and contractible tilt struts in the form of double acting hydraulic actuators or jacks 21, 22 extend upwardly between the push beams 11, 12 and blade 17. When the jacks 21, 22 are both extended the dozer blade will be pitched forwardly about axis 16 and when the jacks 21, 22 are both contracted the blade will be pitched rearwardly. If one of the jacks 21, 22 is either extended or contracted and the other jack is either locked or moved in the opposite direction, the blade 17 will be tilted to a slope cutting condition. When rigid diagonal braces are used between the inner sides of the push beams 11, 12 and the rear of the blade 17, and the blade 17 is tilted from its level cutting position and the rear ends of the push beams will be urged laterally away from one another. Since the rear ends of the push beams 11, 12 cannot move laterally away from each other, because of their connection to the tractor 15, the bush beams are deflected under the stress to which subjected and the conventional diagonal braces are subjected to compressive loading.

In order to prevent the stressing and deflecting of the push beams I provide a pair of special diagonal braces in the form of identical double acting hydraulic jacks 26, 27 which have cylinder components 28, 29, pivotally connected to brackets 31, 32 on the laterally inner sides of push beams 11, 12 and piston components 33, 34, the rod ends of which are universally connected to the lower central rear of the blade 17. The jacks 26, 27 are of a through piston rod design to afford equal displacement pressure chambers 36, 37, 38, 39. The piston components 33, 34 have equal effective pressure areas on opposed sides thereof. The pressure chambers of jacks 26, 27 are cross connected by passage means to cause the jacks 26, 27 to simultaneously contract or expand. As illustrated, the passage means include a first passage or conduit 41 connecting the rod end pressure chamber 36 of jack 26 with the cylinder end pressure chamber 39 of jacks 27 :and a second passage or conduit 42 connecting the cylinder end pressure chamber 37 of jack 26 with the rod end pressure chamber 38 of jack 27.

During a tilting operation both jacks 26, 27 are shortened. No additional load is imposed by the tilting operation since the cross connection of the equal displacement pressure chambers of the jacks 26, 27 permit equal shortening. If the dozer blade is subjected to a sidewise thrust such as illustrated by arrow 46, jack 26 will be subjected to forces tending to lengthen it and jack 27 will be subjected to forces tending to contract it; however, they cannot move in opposite directions because fluid movement is resisted in both jacks. Thus my hydraulic stabilizing system prevents parallelograming of the push beams and blade while permitting simultaneous shortening of the hydraulic jacks during tilting operations of the dozer blade.

There is at least one instance when the push beams should be allowed to have parallelogram movement. This is during alignment of the bulldozer attachment on the tractor. At that time the push beams are aligned and spaced an equal distance from the tracks of a crawler tractor, or the front wheels of a rubber tired tractor, and, also the exact spacing between the rear ends of the push beams is established. In order to make this necessary initial adjustment of the hydraulic bracing system, a bypass passage 46 with shutoff valve 47 is provided. The valve element 48 of valve 47 may be removed to initially fill the system with hydraulic fluid and then screwed part way into the valve housing 49 to permit parallelograming for initial installation or alignment of the bulldozer. After alignment of the bulldozer the valve element 48 is screwed in to its normal shutolf position in which illustrated.

From the foregoing description it will be noted that the braces in the form of jacks 26, 27 cooperate with the push beams 11, 12 and blade 17 to form bracing triangles. The legs of one bracing triangle are formed by jack 26, the part of push beam 11 between pivot pin 51 and pivot pin 18, and the part of blade 17 between pin 18 and ball and socket connection 52. The legs of the other bracing triangle are formed by jack 27. The part of push beam 12 extending between cylinder pivot pin 53 and pin 19 and the part of blade 17 interconnecting pivot pin 19 and the ball end 54 of the rod of jack 27. The present invention achieves simultaneous adjustment of the effective length of corresponding legs of the two bracing triangles.

The illustrated hydraulic stabilizing system effects lateral stability and prevents stressing of dozer components due to tilting of the blade. The system avoids use of exposed mechanical linkage or compensating components which would be apt to wear excessively or malfunction in presence of rocks, debris and other material being excavated or handled.

The embodiments of the invention for which an exclusive property or privilege is claimed are defined as follows:

1. In a tiltable bulldozer including a blade, a pair of laterally spaced push beams having pivotal connections at their forward ends with the blade, tilt struts extending upwardly between the push beams and the blade, at least one of the tilt struts being adjustable in length to effect tilting of the blade, and a pair of diagonal stabilizing braces having pivotal connections at their rear ends 4 with the inner sides of said push beams and having pivot connections at their front ends with the central rear of the blade, the braces, and parts of the push beams and blade extending between the connections forming legs of bracing triangles, the improvement comprising:

a hydraulic actuator in each of a pair of corresponding legs of said triangles having piston and cylinder components defining a pair of pressure chambers, said piston components having opposed effective pressure areas, all of which are equal, and

fluid passage means cross connecting said pressure chambers of said actuators whereby upon moving said blade to a tilt position by adjustment of said one tilt strut said corresponding legs coextensively change in effective length.

2. The structure set forth in claim 1 wherein said corresponding legs are said diagonal braces.

3. The structure set forth in claim 2 wherein said components of said actuators have their ends pivotally connected to said blade and said push beams.

4. The structure set forth in claim 3 wherein said fluid passage means includes a first passage connecting the rod end of one actuator with the cylinder end of the other actuator and a second passage connecting the cylinder end of said one actuator with the rod end of said second actuator and a normally closed bypass passage between said first and second passages and a shutoff valve in said bypass passage having a closed position in which fluid flow through said bypass passage is prevented and an open position in which fluid flow through said bypass passage is permitted.

References Cited UNITED STATES PATENTS 10/1956 Perkins 172-807 X 1/1959 Pereira 172-803 

